Energy resolved STM mapping of C$_{60}$ on metal surfaces: A theoretical study

TL;DR

This theoretical study uses advanced modeling to analyze STM imaging of C60 molecules on metal surfaces, revealing how tip structure influences the observed images and correlating well with recent experimental findings.

Contribution

It provides a detailed theoretical framework combining DFT and nonequilibrium Green's functions to interpret STM images of C60 on metals, including tip effects.

Findings

Molecular orbitals of C60 are clearly identified in energy-resolved maps.

Tip structure and orientation significantly affect STM images.

Theoretical results closely match recent experimental observations.

Abstract

We present a detailed theoretical study of scanning tunneling imaging and spectroscopy of \Csixty on silver and gold surfaces, motivated by the recent experiments and discussion by X. Lu et al. [PRL \textbf{90}, 096802 (2003) and PRB \textbf{70}, 115418 (2004)]. The surface/sample/tip system is described within a self--consistent DFT based tight--binding model. The topographic and conductance images are computed at constant current from a full self--consistent transport theory based on nonequilibrium Green's functions and compared with those simulated from the local density of states. The molecular orbitals of \Csixty are clearly identified in the energy resolved maps, in close correspondence with the experimental results. We show how the tip structure and orientation can affect the images. In particular, we consider the effects of truncated tips on the energy resolved maps.